This invention relates generally to can filling apparatus and methods applicable to the handling of wet food materials, such as blanched spinach. It also relates to apparatus and methods for conveying and feeding such materials to one or more stations where can filling units may be located, and to apparatus and methods for automatically controlling feeding of material.
In my copending application Ser. No. 669,327, filed Mar. 22, 1976 now U.S. Pat. No. 4,019,547 and entitled "Can Filling Method and Apparatus", there is disclosed an apparatus and method which is applicable for filling cans with wet food material, like blanched spinach, with a high degree of accurracy with respect with the weight of material supplied to each can. The apparatus in that instance makes use of an upright tube open at its upper end to receive the wet material, and having means at its lower end to successively cut off equal volumes of the materials for introduction into underlying cans. The upper open end of the tube communicates with a hopper, and feed means delivers the material to a region from which it is dropped into the hopper. More particularly, as shown in said application, the feed means consists of an elevating conveyer which takes the material from the lower supply bin and delivers it to fluffing means overlying the hopper of the tube, which in turn permits the material to drop into the tube. In the operation of such apparatus, it has been customary to provide a supply conveyor which conveys the blanched spinach to the feed bin of one or more of the can filling units. A workman at each station controls operation of a hydraulically powered gate that is moved transversely back and forth over the conveyer belt to fill the feed supply bin. This method has been found objectionable because when one conveyor is supplying, say, eight filling units located at stations distributed along the conveyer, one or more of the stations may not receive sufficient spinach for continuous uninterrupted operation.
The claw type elevating conveyer disclosed in said U.S. Pat. No. 4,019,547 Ser. No. 669,327 which raises the spinach from the feed bin to a level above the hopper connected to the tube is arranged to drop the spinach on the rotating fluffer. A rake-off conveyer is disposed immediately above the discharge end of the elevating conveyor and is driven at a speed somewhat greater than that of the elevating conveyer, whereby the material is dragged off the end of the elevating conveyer and dropped upon the fluffer. It has been found that this type of feed arrangement is subject to variations in the rate of feed, thus complicating the problem of maintaining the column of material in the upright tube at a constant height. In addition the claw type of elevating conveyer is expensive and difficult to keep clean.
For the purpose of automatically maintaining a column of material of constant height in the tube of the can filling assembly, pneumatic sensors are disclosed in said U.S. Pat. No. 4,019,587 Ser. No. 669,327, which function to shut off the drive to the elevating conveyer when the column of material exceeds a predetermined height. It has been found that this type of control is not as sensitive or reliable as desired, which is attributed in part to condensation of moisture in the small passages or orifices through which air is discharged into one side of the vertical tube. In addition, such a sensing arrangement requires use of a tube sufficiently long to provide an extension at its upper end where the sensing devices are located.